The field of the invention relates to increasing the warm-up rate of the catalytic converter after engine start by controlling the engine's ignition timing and air/fuel ratio.
It is known to retard engine ignition timing for a predetermined time after engine start to more rapidly warm-up the catalytic converter. U.S. Pat. No. 4,144,853 discloses a system in which ignition timing is retarded until a temperature measurement of the catalytic converter reaches a predetermined temperature.
The inventors herein have recognized numerous problems with the above approaches. For example, engine power and fuel economy are reduced while the ignition timing is retarded. If ignition timing is retarded longer than necessary to achieve a desired catalytic converter efficiency, fuel economy and engine power are needlessly wasted.